The present invention relates to systems and processes for obtaining a Clostridial neurotoxin, methods for making a pharmaceutical composition therefrom and to therapeutic and cosmetic uses of the pharmaceutical composition so made. In particular, the present invention relates to a rapid, animal protein free, chromatographic process and system for obtaining a high potency, high purity, and high yield biologically active botulinum neurotoxin.
A pharmaceutical composition suitable for administration to a human or animal for a therapeutic, diagnostic, research or cosmetic purpose comprises an active ingredient and one or more excipients, buffers, carriers, stabilizers, tonicity adjusters, preservatives and/or bulking agents. The active ingredient in a pharmaceutical composition can be a biologic such as a botulinum neurotoxin. Known methods (such as the Schantz method) for obtaining a botulinum neurotoxin useful as the active ingredient in a pharmaceutical composition are multi-week culturing, fermentation and purification processes which use animal-derived proteins, such as meat broth and casein used in culture and fermentation media, and animal derived purification enzymes. Administration to a patient of a pharmaceutical composition made through use of animal derived products can entail risk of administering pathogens or an infectious agent, such as a prion. Additionally, known animal protein free methods for obtaining a botulinum toxin are also time-consuming processes (i.e. take more than a week to complete) with numerous upstream (culturing and fermentation) and downstream (purification) steps, and yet still result in obtaining a botulinum neurotoxin with detectable impurities.
Botulinum Toxin
The genus Clostridium has more than one hundred and twenty seven species, grouped by morphology and function. The anaerobic, gram positive bacterium Clostridium botulinum produces a potent polypeptide neurotoxin, botulinum toxin (synonymously “toxin”), which causes a neuroparalytic illness in humans and animals known as botulism. Symptoms of botulinum toxin intoxication can progress from difficulty walking, swallowing, and speaking to paralysis of the respiratory muscles and death.
One unit of botulinum toxin is defined as the LD50 upon intraperitoneal injection into female Swiss Webster mice weighing about 18-20 grams each. One unit of botulinum toxin is the amount of botulinum toxin that kills 50% of a group of female Swiss Webster mice. Seven generally immunologically distinct botulinum neurotoxins have been characterized, these being respectively botulinum neurotoxin serotypes A, B, C1, D, E, F and G each of which is distinguished by neutralization with type-specific antibodies. The different serotypes of botulinum toxin vary in the animal species that they affect and in the severity and duration of the paralysis they evoke. The botulinum toxins apparently bind with high affinity to cholinergic motor neurons and translocate into the neuron and block the presynaptic release of acetylcholine.
Botulinum toxins have been used in clinical settings for the treatment of e.g. neuromuscular disorders characterized by hyperactive skeletal muscles. Botulinum toxin type A has been approved by the U.S. Food and Drug Administration (FDA) for the treatment of essential blepharospasm, strabismus and hemifacial spasm in patients over the age of twelve, cervical dystonia, glabellar line (facial) wrinkles and for treating hyperhydrosis. The FDA has also approved a botulinum toxin type B for the treatment of cervical dystonia.
Although all the botulinum toxins serotypes apparently inhibit release of the neurotransmitter acetylcholine at the neuromuscular junction, they do so by affecting different neurosecretory proteins and/or cleaving these proteins at different sites. Botulinum toxin type A is a zinc endopeptidase which can specifically hydrolyze a peptide linkage of the intracellular, vesicle-associated protein (VAMP, also called synaptobrevin) 25 kiloDalton (kDa) synaptosomal associated protein (SNAP-25). Botulinum type E also cleaves SNAP-25 but targets different amino acid sequences within this protein, as compared to botulinum toxin type A. Botulinum toxin types B, D, F and G act on VAMP with each serotype cleaving the protein at a different site. Finally, botulinum toxin type C1 has been shown to cleave both syntaxin and SNAP-25. These differences in mechanism of action may affect the relative potency and/or duration of action of the various botulinum toxin serotypes.
The molecular weight of the active botulinum toxin protein molecule (also known as “pure toxin” or as the “neurotoxic component”) from a botulinum toxin complex, for all seven of the known botulinum toxin serotypes, is about 150 kDa. Interestingly, the botulinum toxins are released by Clostridial bacterium as complexes comprising the 150 kDa neurotoxic component along with one or more associated non-toxin proteins. Thus, the botulinum toxin type A complex can be produced by Clostridial bacterium as 900 kDa, 500 kDa and 300 kDa forms (approximate molecular weights). Botulinum toxin types B and C1 are apparently produced as only a 500 kDa complex. Botulinum toxin type D is produced as both 300 kDa and 500 kDa complexes. Finally, botulinum toxin types E and F are produced as only approximately 300 kDa complexes. The complexes (i.e. molecular weight greater than about 150 kDa) contain hemagglutinin (HA) proteins and a non-toxin non-hemagglutinin (NTNH) protein. Thus, a botulinum toxin complex can comprise a botulinum toxin molecule (the neurotoxic component) and one or more HA proteins and/or NTNH protein. These two types of non-toxin proteins (which along with the botulinum toxin molecule can comprise the relevant neurotoxin complex) may act to provide stability against denaturation to the botulinum toxin molecule and protection against digestive acids when toxin is ingested. Additionally, it is possible that the larger (greater than about 150 kDa molecular weight) botulinum toxin complexes may result in a slower rate of diffusion of the botulinum toxin away from a site of intramuscular injection of a botulinum toxin complex. The success of botulinum toxin type A to treat a variety of clinical conditions has led to interest in other botulinum toxin serotypes. Thus, at least botulinum toxins types, A, B, E and F have been used clinically in humans. Additionally, a formulation of the neurotoxic component (i.e. without the associated non-toxin proteins) is sold in Europe under the tradename XEOMIN (Merz Pharmaceuticals, Frankfurt, Germany).
The botulinum toxin type A is known to be soluble in dilute aqueous solutions at pH 4-6.8. At pH above about 7 the stabilizing non-toxin proteins dissociate from the neurotoxin, resulting in a gradual loss of toxicity, particularly as the pH and temperature rise (Schantz E. J., et al Preparation and characterization of botulinum toxin type A for human treatment (in particular pages 44-45), being chapter 3 of Jankovic, J., et al, Therapy with Botulinum Toxin, Marcel Dekker, Inc, 1994).
As with enzymes generally, the biological activities of the botulinum toxins (which are intracellular peptidases) are dependant, at least in part, upon their three dimensional conformation. Dilution of the toxin from milligram quantities to a solution containing nanograms per milliliter presents significant difficulties, such as, for example, tendency for toxin to adhere to surfaces and thus reduce the amount of available toxin. Since the toxin may be used months or years after the toxin containing pharmaceutical composition is formulated, the toxin is stabilized with a stabilizing agent such as albumin, sucrose, trehalose and/or gelatin.
A commercially available botulinum toxin containing pharmaceutical composition is sold under the trademark BOTOX® (botulinum toxin type A purified neurotoxin complex) available commercially from Allergan, Inc., of Irvine, Calif. Each 100 unit vial of BOTOX® consists of about 5 ng of purified botulinum toxin type A complex, 0.5 mg human serum albumin, and 0.9 mg sodium chloride, vacuum-dried form and intended for reconstitution with sterile normal saline without a preservative (0.9% sodium chloride injection). Other commercially available, botulinum toxin-containing pharmaceutical compositions include Dysport® (Clostridium botulinum type A toxin hemagglutinin complex with human serum albumin and lactose in the botulinum toxin pharmaceutical composition), available from Ipsen Limited, Berkshire, U.K. as a powder to be reconstituted with 0.9% sodium chloride before use), and MyoBloc™ (an injectable solution comprising botulinum toxin type B, human serum albumin, sodium succinate, and sodium chloride at about pH 5.6, available from Solstice Neurosciences of San Diego, Calif. The neurotoxic component (the 150 kDa toxin molecule) and botulinum toxin complexes (300 kDa to 900 kDa) can be obtained from, for example, List Biological Laboratories, Inc., Campbell, Calif.; the Centre for Applied Microbiology and Research, Porton Down, U.K.; Wako (Osaka, Japan), as well as from Sigma Chemicals of St Louis, Mo.
Animal protein free and/or chromatographic methods for obtaining a botulinum neurotoxin are disclosed in U.S. Pat. Nos. 7,445,914; 7,452,697; 7,354,740; 7,160,699; 7,148,041, and; 7,189,541. Also of interest are U.S. patent application Ser. Nos. 11/609,449 entitled “Media for Clostridium Bacterium”, filed Dec. 12, 2006; 12/098,896 entitled “Animal Product Free Media and Processes for Obtaining a Botulinum Toxin”, filed Apr. 7, 2008; 11/932,689 entitled “Chromatographic Method and System for Purifying a Botulinum Toxin”, filed Oct. 31, 2007; 11/932,789 entitled “Chromatographic Method and System for Purifying a Botulinum Toxin” filed Oct. 31, 2007, and; 12/234,537, entitled “Animal Product Free Media And Processes For Obtaining A Botulinum Toxin”, filed Sep. 19, 2008.
Botulinum toxin for use in a pharmaceutical composition can be obtained by anaerobic fermentation of Clostridium botulinum using the well known Schantz process (see e.g. Schantz E. J., et al., Properties and use of botulinum toxin and other microbial neurotoxins in medicine, Microbiol Rev 1992 March; 56(1):80-99; Schantz E. J., et al., Preparation and characterization of botulinum toxin type A for human treatment, chapter 3 in Jankovic J, ed. Neurological Disease and Therapy. Therapy with botulinum toxin (1994), New York, Marcel Dekker; 1994, pages 41-49, and; Schantz E. J., et al., Use of crystalline type A botulinum toxin in medical research, in: Lewis GE Jr, ed. Biomedical Aspects of Botulism (1981) New York, Academic Press, pages 143-50). The Schantz process for obtaining a botulinum toxin makes use of animal products for example as reagents and as part of the culture and fermentation media.
A number of steps are required to make a Clostridial toxin pharmaceutical composition suitable for administration to a human or animal for a therapeutic, diagnostic, research or cosmetic purpose. These steps can include obtaining a purified Clostridial toxin and then compounding the purified Clostridial toxin. A first step can be to plate and grow colonies of Clostridial bacteria, typically on blood agar plates, in an environment conducive to anaerobic bacterial growth, such as in a warm anaerobic atmosphere. This step allows Clostridial colonies with desirable morphology and other characteristics to be obtained. In a second step selected Clostridial colonies can be fermented in a first suitable medium and if additionally desired, into a second fermentation medium. After a certain period of fermentation, the Clostridial bacteria typically lyse and release Clostridial toxin into the medium. Thirdly, the medium can be purified so as to obtain a bulk toxin. Typically medium purification to obtain bulk toxin is carried out using, among other reagents, animal-derived enzymes, such as DNase and RNase, which are used to degrade and facilitate removal of nucleic acids. The resulting bulk toxin can be a highly purified toxin with a particular specific activity. After stabilization in a suitable buffer, the bulk toxin can be compounded with one or more excipients to make a Clostridial toxin pharmaceutical composition suitable for administration to a human. The Clostridial toxin pharmaceutical composition can comprise a Clostridial toxin as an active pharmaceutical ingredient (API). The pharmaceutical composition can also include one or more excipients, buffers, carriers, stabilizers, preservatives and/or bulking agents.
The Clostridium toxin fermentation step can result in a fermentation medium solution that contains whole Clostridium bacteria, lysed bacteria, culture medium nutrients and fermentation by-products. Filtration of this culture solution so as to remove gross elements, such as whole and lysed bacteria, provides a harvest/clarified medium. The clarified medium comprises a Clostridial toxin and various impurities and is processed to obtain a concentrated Clostridial toxin, which is called bulk toxin.
Fermentation and purification processes for obtaining a bulk Clostridial toxin using one or more animal derived products (such as the milk digest casein, DNase and RNase) are known. An example of such a known non-animal product free (“NAPF”) process for obtaining a botulinum toxin complex is the Schantz process and modifications thereto. The Schantz process (from initial plating, cell culture through to fermentation and toxin purification) makes use of a number of products derived from animal sources such as, for example, animal derived Bacto Cooked Meat medium in the culture vial, Columbia Blood Agar plates for colony growth and selection, and casein in the fermentation media. Additionally, the Schantz bulk toxin purification process makes use of DNase and RNase from bovine sources to hydrolyze nucleic acids present in the toxin containing fermentation medium. Concerns have been expressed regarding a potential for a viral and transmissible spongiform encephalopathy (TSE), such as a bovine spongiform encephalopathy (BSE), contamination when animal products are used in a process for obtaining an API and/or in a process for making (compounding) a pharmaceutical composition using such an API.
A fermentation process for obtaining a tetanus toxoid that uses reduced amounts of animal-derived products (referred to as animal product free or “APF” fermentation processes; APF encompasses animal protein free) is known, see e.g. U.S. Pat. No. 6,558,926. An APF fermentation process for obtaining a Clostridial toxin, has the potential advantage of reducing the (the already very low) possibility of contamination of the ensuing bulk toxin with viruses, prions or other undesirable elements which can then accompany the active pharmaceutical ingredient, Clostridial toxin, as it is compounded into a pharmaceutical composition for administration to humans.
Chromatography, such as column chromatography for example, can be used to separate a particular protein (such as a botulinum neurotoxin) from a mixture of proteins, nucleic acids, cell debris, etc. in a process known as fractionation or purification. The protein mixture typically passes through a glass or plastic column containing, for example, a solid, often porous media (often referred to as beads or resin). Different proteins and other compounds pass through the matrix at different rates based on their specific chemical characteristics and the way in which these characteristics cause them to interact with the particular chromatographic media utilized.
The choice of media determines the type of chemical characteristic by which the fractionation of the proteins is based. There are four basic types of column chromatography; ion-exchange, gel filtration, affinity and hydrophobic interaction. Ion-exchange chromatography accomplishes fractionation based on surface electrostatic charge using a column packed with small beads carrying either a positive or a negative charge. In gel filtration chromatography, proteins are fractionated based on their size. In affinity chromatography, proteins are separated based on their ability to bind to specific chemical groups (ligand) attached to beads in the column matrix. Ligands can be biologically specific for a target protein. Hydrophobic interaction chromatography accomplishes fractionation based on surface hydrophobicity.
Column chromatography to purify (fractionate) a Clostridial toxin is well known. See for example the following publications:    1. Ozutsumi K., et al, Rapid, simplified method for production and purification of tetanus toxin, App & Environ Micro, April 1985, p 939-943, vol 49, no. 4. (1985) discloses use of high pressure liquid chromatography (HPLC) gel filtration to purify tetanus toxin.    2. Schmidt J. J., et al., Purification of type E botulinum neurotoxin by high-performance ion exchange chromatography, Anal Biochem 1986 July; 156(1):213-219 discloses use of size exclusion chromatography or ion exchange chromatograph to purify botulinum toxin type E. Also disclosed is use of protamine sulfate instead of ribonuclease (RNase).    3. Simpson L. L., et al., Isolation and characterization of the botulinum neurotoxins Simpson L L; Schmidt J J; Middlebrook J L, In: Harsman S, ed. Methods in Enzymology. Vol. 165, Microbial Toxins: Tools in Enzymology San Diego, Calif.: Academic Press; vol 165: pages 76-85 (1988) discloses purification of botulinum neurotoxins using gravity flow chromatography, HPLC, capture steps using an affinity resin, size exclusion chromatography, and ion (anion and cation) exchange chromatography, including use of two different ion exchange columns. Various Sephadex, Sephacel, Trisacryl, S and Q columns are disclosed.    4. Zhou L., et al., Expression and purification of the light chain of botulinum neurotoxin A: A single mutation abolishes its cleavage of SNAP-25 and neurotoxicity after reconstitution with the heavy chain, Biochemistry 1995; 34(46):15175-81 (1995) discloses use of an amylose affinity column to purify botulinum neurotoxin light chain fusion proteins.    5. Kannan K., et al., Methods development for the biochemical assessment of Neurobloc (botulinum toxin type B), Mov Disord 2000; 15(Suppl 2):20 (2000) discloses use of size exclusion chromatography to assay a botulinum toxin type B.    6. Wang Y-c, The preparation and quality of botulinum toxin type A for injection (BTXA) and its clinical use, Dermatol Las Faci Cosm Surg 2002; 58 (2002) discloses ion exchange chromatography to purify a botulinum toxin type A. This reference discloses a combination of precipitation and chromatography techniques.    7. Johnson S. K., et al., Scale-up of the fermentation and purification of the recombination heavy chain fragment C of botulinum neurotoxin serotype F, expressed in Pichia pastoris, Protein Expr and Purif 2003; 32:1-9 (2003) discloses use of ion exchange and hydrophobic interaction columns to purify a recombinant heavy chain fragment of a botulinum toxin type F.    8. Published U.S. patent application 2003 0008367 A1 (Oguma) discloses use of ion exchange and lactose columns to purify a botulinum toxin.
The purification methods summarized above relate to small-scale purification of the neurotoxic component of a botulinum toxin complex (i.e. the approximately 150 kDa neurotoxic molecule), or a specific component of the neurotoxic component, as opposed to purification of the entire 900 kDa botulinum toxin complex.
Furthermore, existing processes, including commercial scale processes, for obtaining a botulinum toxin suitable for compounding into a botulinum toxin pharmaceutical composition typically include a series of precipitation steps to separate the toxin complex from impurities that accompany the botulinum toxin from the fermentation process. Notably, precipitation techniques are widely used in the biopharmaceutical industry to purification a botulinum toxin. For example, cold alcohol fractionation (Cohn's method) or precipitation is used to remove plasma proteins. Unfortunately, previous precipitation techniques for purifying a botulinum toxin have the drawbacks of low resolution, low productivity, difficulty of operation, difficulty to control and/or validate and/or difficulty to scale-up or scale-down. Previously published U.S. patent application Ser. No. 11/452,570, published Oct. 12, 2006, discloses steps such as centrifugation, acid precipitation, ethanol precipitation, acidification steps, and ammonium sulfate precipitation utilized in various animal-protein free and NAPF processes (for a detailed discussion, see U.S. Published Patent App. No. 2006/0228780, herein incorporated by reference in its entirety). Some distinctions between a non-animal protein free process and an animal protein free processes for obtaining a botulinum neurotoxin are shown therein.
What are needed therefore are rapid, relatively smaller scale yet high yield systems and processes for obtaining high purity, highly potent botulinum neurotoxin, which can be used for research purposes and/or to make a pharmaceutical composition.